On Thu, Oct 05, 2006 at 08:14:35 +0200, David Olofson wrote: > On Thursday 05 October 2006 19:59, Paul Winkler wrote: > > On Thu, Oct 05, 2006 at 07:07:34PM +0200, Fons Adriaensen wrote: > > > On Thu, Oct 05, 2006 at 05:12:20PM +0100, Steve Harris wrote: > > > > > > > The SC* plugins do the same as TAP (calculate the gain every 4 > > > > samples), > > > > but I interpolate the gain values between each computation. The > > > > attch/deacay times were slow enough in my testing that it was OK > > > > to do > > > > that. > > > > > > It should be OK for all practical attack/release times. The only > > > penalty is 3 samples of delay on the gain change and maybe that's > > > to be avoided for a hard limiter. For a normal compressor it > > > should not matter. > > > > That is what, 90 microseconds at 44.1 kHz? I don't think there are > > any analog compressors that react anywhere near that fast. Don't > > worry about it :-) > > I don't know how fast it *actually* is, but FWIW, my old Behringer > compressor/limiter has a lowest attack setting of 0.1 ms, and a > lowest release setting of 50 ms.
So that would be a little iffy. SC4 only advertises that it goes down to 1.5ms, which gives something like 90 segments in the attack segment. Looking at the code, the compressors use a pretty expensive linear -> dB conversion routine (cubicly interpolated lookup table) to work out the gain changes, maybe I could substitute a cheap approximation function. I'll bet that analogue compressors didn't use accurace logarithmic approximations. I'm not sure It'd be worth dropping the calcualtion period below 2 though. - Steve